Opened 4 years ago
Closed 3 years ago
#26189 closed defect (fixed)
Intersection of modular abelian varieties gives wrong answer
Reported by: | klui | Owned by: | |
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Priority: | major | Milestone: | sage-8.8 |
Component: | modular forms | Keywords: | |
Cc: | Merged in: | ||
Authors: | Kevin Lui | Reviewers: | Travis Scrimshaw |
Report Upstream: | N/A | Work issues: | |
Branch: | 94b9fdd (Commits, GitHub, GitLab) | Commit: | 94b9fddbaa4a883e88ad4c3e089332506692a8c5 |
Dependencies: | Stopgaps: |
Description
The intersection code is sometimes wrong. Here's an example:
This is the setup:
sage: d1 = J0(11).degeneracy_map(22, 1) sage: d2 = J0(11).degeneracy_map(22, 2) sage: A = (d1-d2).image() sage: J = J0(22)
This is correct:
sage: J.intersection(A) (Finite subgroup with invariants [] over QQbar of Abelian variety J0(22) of dimension 2, Abelian subvariety of dimension 1 of J0(22))
This is wrong:
sage: A.intersection(J) (Finite subgroup with invariants [2] over QQbar of Abelian subvariety of dimension 1 of J0(22), Abelian subvariety of dimension 1 of J0(22))
Change History (9)
comment:1 Changed 4 years ago by
comment:2 Changed 3 years ago by
- Branch set to u/klui/intersection
comment:3 Changed 3 years ago by
- Commit set to f8f372378591c234e574b6dd3e99e768ae8da1f8
- Status changed from new to needs_review
No code change here. Just a documentation update.
The intersection of 2 abelian varieties, X and Y, is G+A, where G is a finite subgroup with an element in each component and A is the identity component. I don't think there's a canonical way to choose G so that it's a subgroup of X or Y.
New commits:
f8f3723 | Added documentation explaining what intersection does.
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comment:4 Changed 3 years ago by
- Commit changed from f8f372378591c234e574b6dd3e99e768ae8da1f8 to 320ffbbfcf8596bf40ef5c5426e061886f26baef
Branch pushed to git repo; I updated commit sha1. New commits:
320ffbb | doc error
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comment:5 Changed 3 years ago by
comment:6 Changed 3 years ago by
- Milestone changed from sage-8.4 to sage-8.8
- Reviewers set to Travis Scrimshaw
A little tweak to get the punctuation correct:
- canonical. (see :trac:`26189`). In this following example, ``B`` is a - subvariety of ``J``.:: + canonical (see :trac:`26189`). In this following example, ``B`` is a + subvariety of ``J``::
Once done, you can set a positive review on my behalf.
comment:7 Changed 3 years ago by
- Commit changed from 320ffbbfcf8596bf40ef5c5426e061886f26baef to 94b9fddbaa4a883e88ad4c3e089332506692a8c5
Branch pushed to git repo; I updated commit sha1. New commits:
94b9fdd | punctuation fix as suggested by Travis Scrimshaw
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comment:8 Changed 3 years ago by
- Status changed from needs_review to positive_review
Fixed. Thanks for the review!
comment:9 Changed 3 years ago by
- Branch changed from u/klui/intersection to 94b9fddbaa4a883e88ad4c3e089332506692a8c5
- Resolution set to fixed
- Status changed from positive_review to closed
#6392 ?